The class of polysaccharides is recognized to be of paramount importance in modern technology; the possible molecular chemodiversity of these biomaterials that can be found in microalgae can play an important role in industrial sectors such as food, pharmaceutical, cosmetic, nutraceutical, and aquaculture. Some species of microalgae are already commercially available and studies about their bioculturing are advanced, thus offering high-value products for commercial applications. In this chapter the results of a searching the literature from 2013 to 2019 has been conducted on the structural identification and characterization of polysaccharides from these microorganisms. This report has been restricted to species commercially available, which are well known and prone to possible utilization and will not cover any possible discovery about rare or new species. In addition, prompted by the recent sudden outbreak of COVID-19, some literature reports on antiviral potential of microalgae polysaccharides among the commercial species are underlined. The overall results of this analysis seem not encouraging about flourishing of new detailed knowledge of fine structural features of these polysaccharides. The situation is reflecting the historical one observed for the launch of polysaccharides in biotechnology since 1950s. Intensive studies on possible exploitation using crude or partially purified and hardly standardized biomass preexisted to more demanding applications with standardized preparations with possible applications in more demanding fields. Only an interdisciplinary effort can lead soon to research for new chemical knowledge on fine structural details that are necessary to increase possible extensions of applications of pure material.